1. Field of the Invention
The present invention relates to methods and wireless systems for sensing the location of an ambulatory subject such as a living being (e.g., a person or animal) and for constraining a subject to a specific area.
2. Discussion of the Prior Art
Many pet owners are familiar with devices known as “invisible fences” which can be used in conjunction with training collars that measure proximity to buried wires. Burying the wires is expensive and inconvenient, however, and, once done, limits the training ground to the area within a buried wire perimeter. Actual, physical fence structures are even less convenient.
The invisible fence devices include a training collar with a device that reacts to a pre-installed, fixed electrical induction loop of buried wire, which defines the operating boundaries (e.g., of a training area). The constraint by a fence is physical, while the so-called invisible fence or induction loop activates an impulse within the band worn by the subject. This usually involves a slightly painful alert to the subject, signaling that the subject has crossed a border. Such installations are impractical when the limits are very large and virtually useless when involving water-covered areas or when the borders need to be variable and adjustable or when the training area must be designed extemporaneously.
The prior art also includes many radio proximity devices which can be used to emit an audible signal or provide an electric shock in response to a detected change in received radio signal strength.
These prior art methods require the trainer to choose an area and are not well suited to conducting training exercises in the field, wherever one may be.
The prior art also includes training devices used to monitor behavior of dogs and the like (such as U.S. Pat. Nos. 6,263,836 and 6,487,992 to R. L. Hollis), but they do not address all of the problems identified by the applicants.
There is a need, therefore, for an economical, and convenient, yet effective, method for training dogs, other animals and people which does not require burying wires in an area before training can begin.